An Evaluation of Tornado Intensity Using Velocity and Strength Attributes from the WSR-88D Mesocyclone Detection Algorithm

One of the major goals of the WeatherReady Nation is for the NWS and its partners to provide the appropriate impact-based decision support warning services to mitigate negative outcomes from specific hazard threats. In order to accomplish this for tornado hazards, a forecaster could benefit from guidance to assess the strength of ongoing tornadoes. This study hopes to address whether such guidance is feasible by an exploratory comparison of MDA attributes generated from super-resolution data with the intensity of tornadoes rated by the EF-scale. We evaluated over 350,000 mesocyclone detections from the WSR-88D MDA and performed spatial and temporal checking against over 3900 EF-rated tornado segments surveyed by National Weather Service (NWS) employees from 2009 through 2011. Matching detections had their algorithm-derived parameters of Low-Level Rotational Velocity (LLVR), Strength Rank (SR), and vertically integrated Mesocyclone Strength Index (MSI) extracted and mapped to the EF-rating of the tornado segment. Once mapped, the maximum value and mean of the top three values for each parameter were compared to values from other individual and groups of EF-ratings through distribution analyses and bootstrapped contingency tables. In order to account for sampling issues at further ranges from the radar, the analyses were broken out into 20km range bins and re-run for the 55 different bin permutations of detections 0km-200km from the radar. Findings from these analyses will be presented.